Processing, thermoplastics hydraulic pressure

Second, the low melt viscosity of SPS formulations helps to reduce molded-in stress from the injection molding process. The data in Figure 15.7 show typical melt viscosities of SPS in comparison with other semicrystalline thermoplastics. The low melt viscosity of SPS results in low hydraulic pressures during injection molding, which helps to minimize molded-in stress. Low viscosity also contributes to SPS s ability to fill complex parts with thin walls and its relative lack of flash during injection molding. 

Solid phase forming or forging is a process wherein a heated blank of thermoplastic material is placed in a female die with a male punch and reformed under impact or high compression pressure. Hydraulic or toggle presses are used to form the simple shapes shown in Fig. 9-26. This process is commonly used for thick section parts, for example, wide face gears made of thermoplastics. Such pieces would have a... 

Some polyurethane materials (e.g., flexible foams with a small degree of crosslinking or monolithic thermoplastic polyurethanes) can be processed by methods typical of thermoplastic polymers. Compression molding in a hydraulic press is most often used to this purpose. At high temperature and pressure, the crosslinks are broken and the material flows in the mold. In this way,... 

---